The art of modular base building

[Temstar]

Let's have some pictures first to fire up the imagination:

Mun Fuel Terminal:

Prototype Mun Base:

Prototype Kethane Refinary:

So, how are these bases built? Let's break that question down into a series of smaller question.

1. How do I move modules around?

I know some people prefer mobile cranes to lift modular base pieces into location. I prefer the "bottom loader" concept where each piece of a base is equipped with a 1.25m docking port underneath arranged in such a way so that when the landing legs are deployed there is just enough clearance for this rover (I refer to it as the "Base Crawler") to slip in underneath:

A gap of around this size is acceptable. You don't have to be millimetre perfect with this technique. Once you drive the rover under your module you can really feel the magnetic attraction. Even on Kerbin the attraction between the docking ports is enough to pull the rover so that it tends to go backwards and forwards under the module without any user input. To centre your rover exactly underneath just apply slight forward motion when the docking ports are pulling you backwards and then a tap backwards when the docking port is pulling you forward. Eventually your rover will stop dead centre under the module. Then you just switch to the module and retract the landing legs.

The drop will also correct small amount of misalignment. When done right the module will drop on the rover and the two will merge into one craft. You can then use the rover to move the pieces around. Should you miss up just hit G again to deploy the legs again and start over.

2. How do I line up the docking ports, both bottom and side?

I firmly believe that to be called a "base", the base components need to be merged as a single craft. We can then pretend the base residence can move around inside in a shirt sleeve environment rather than spend two hours putting on an EVA suit just go pop next door. If you look carefully at the three pictures at the top of the post you notice that my bases are laid out so there is a framework of pipes or base tunnels, onto which individual modules are attached. So how do I make sure when I move these piece into position and lower their landing legs the docking ports will line up?

First, the pipes:

Here we see a single five segment straight tunnel in the VAB. Note the landing legs - the are place in pairs in the SPH in lateral symmetry with angle snap on. The legs are pointed directly up and so make a tangent with the 1.25m tube right where its walls are vertical to the ground. That means suppose we assume the landing legs prop up stuff at a height of X meters when deployed, we immediately know that centre of the docking port is X meters off ground when this pipe is deployed, and so any other structure where its horizontal docking port will end up X meters off the ground at its centre will be compatible with this pipe. We'll define this as "standard base height"

What does that mean? Suppose we have this structure:

We immediately know, without even having to test that this structure is compatible with the pipe above. So if we nudge the two so that the docking port on their ends touch they will be on the exact same height (let's ignore uneven ground and weight of structure for now) and snap together. If you have a round piece and you place large landing legs with angle snap so they point directly up and then you place docking ports on the ends, that docking port will always be "standard base height" regardless of actual diameter of the round piece. So using this simple fact we can build base tunnels of almost any shape and know they will fit together at "standard base height" without even having to test them:

Now obviously you need a docking port under your pipe piece for the base crawler to dock with it to carry it around. Since we know that pipes are always going to stand up at one standard base height we know exactly how much the docking port need to reach down for the correct amount of clearance to mate with the base crawler. Above is what I use for my 1.25m pipes - one radial attachment point, one 1.25m remote guidance unit and the one downward facing docking port gives just about the perfect clearance. The guidance unit gives the pipe the controllability to extend and retract landing legs when it's not connected to anything, at least until it's internal battery is flat. Remember you want to have this downward docking port at centre of mass of your pipe, or else its going to be hard to drive around!

Okay well that's easy, but what about the base modules? They're not horizontal 1.25m or 2.5m pieces, they're standing vertically! How do I align my docking ports so that the docking ports on the base modules are at standard base height?

Unfortunately for the bottom docking port there is no easy way to know how much clearance you have. The only way is to test repeatedly by putting the module on the launch pad, deploy the legs and drive the Base Crawler (I put it on the runway and drive it over to the launch pad) underneath and see how well the docking ports line up. If there is too much room then you have to move the landing legs higher on your module. If there isn't enough room for the rover to drive underneath then you have to lower the attach point of the landing legs on your mobile. Repeat this until you get right.

Fortunately there is an easy way to make sure the horizontal docking port are at standard base height without going to the trouble of driving it off the launch pad and testing it up against a pipe or another module:

Here we have a new module I'm working on - a simple 6400L fuel tank module. I've already done the test to make sure the landing legs give the correct bottom clearance. So what's left is working out if that horizontal docking port is correctly aligned. I do that by grabbing another structural fuselage piece and attach it underneath, then put a single large landing strut on it as if I'm building a pipe. Then I do this:

Grab that fuselage piece and stick it on the docking port being aligned. Then adjust your view so that you virtual eye level is exactly level with some part of a landing strut on your module. The grab the docking port and move it up or down so that the part of the landing leg on the fuselage corresponding with your alignment element is exactly flat, as the case here illustrated by the blue line.

Place that docking port and there you have it. That docking port is now set to standard base height when the landing struts on the module deploys, no other test is required. You can get rid of that fuselage and save the part and be assured that it's compatible with other module base parts.

3. I did what you said but my piece still doesn't line up in the field!

(I know this connection is not standard base height, but the exaggerated nature makes it easy to get the point, plus the cause is the same)

Sometimes, even though you've done all your measurement and alignment correctly in the VAB/SPH, when you actually try to build a base in practice this happens. The reason is because of the technique. What's actually happening here is the weight of your module is messing with suspension on the Base Crawler (or tanker rover in this case). When you line up the docking ports for standard base height the assumption is that both pieces you're trying to connect are setting on perfectly rigid support. When you actually do this in practice this ends up not being true. If your module is very heavy as is the case here it will actually squash down on the rover's suspension and make the docking port lower by a bit. Add to this the little drop you get when you drop the module onto the rover and you'll usually end up a situation where the docking port on the piece you're trying to dock is lower than the available docking port on the base. This problem is worse on Kerbin due to higher gravity than it is on say the Mun. But even there it still exists if you're moving full 6400L fuel tanks or other similar heavy modules. Fortunately there is a simple way to get around this:

What you do is park your module right up against the docking port, switch to the base and raise the landing struts on the structures (usually that means legs on pipes) closest to your new module. This causes that section to droop down a bit due to gravity. And during its downward travel if it goes low enough it will find the docking port on your new module and it will become attached. Then it's a simple matter of deploying all legs and undock the Base Crawler.

I am currently working on a major Mun base, once done and I've made sure all the launch vehicles for my modules are Mun-capable and all the pictures are gathered I'll release all my base modules as a set. For now here's craft files for my Base Crawler, and two example lifters for base tunnels.

http://www./view/w0p0eumhsh6r932/Base_Crawler.craft

http://www./view/fzr6pucl79m32sj/Base_Part_Transpoter.craft

http://www./view/5l2nls223xenc05/Base_Part_Transpoter_2.craft

Edited September 5, 2013 by Temstar

[LeadMagnet]

Excellent post! Well done, very clear pictures as well AND the inclusion of CRAFT files!! All I need now is a world save with the base already in place on the Mun! Just kidding!

Very, VERY well done sir!

[Specialist290]

Nicely done! I've been thinking about doing some base-building of my own recently, and I'm sure this tutorial will help me considerably with getting everything just right.

[KatzOhki]

Very good tutorial! My major problem is weight too, but I'm docking big rovers end to end...

[Hallofo]

Awesome guide! I'll most certainly be trying this out soon. I had never considered using rover parts like that to move stuff around. Previously, I had MJ to land parts "close enough" and then RCS-hop my way over.

[Talonsin]

When I see screenings like your it makes me realize just how much I suck at this game. Lol

[Dangerous_Beans]

How much weight can the little rover take?

is it able to move those full jumbo cans around on Kerbin?

i was trying to do this last night, and failing, so this should be really helpful. thanks

[JiWint]

I still don't get how to I build docking ports in vab (or sph) so that the parts will align good enough?

[wilt57]

I still don't get how to I build docking ports in vab (or sph) so that the parts will align good enough?

Just use a simple relationship between the docking port and the landing legs. If you use all the same legs and line them up with the docking ports on your pieces, they will line up with other pieces. The legs have a standard height, both deployed and stowed. Place them at the same height as your docking ports.

[Sprool]

excellent post, huge help - i'm off to make stuff........

[togfox]

So, now that the legs are hydraulic and no longer fixed length, what's the new method of modular basing?

[dpraptor]

Wow - awesome!! This has been the biggest problem with base building. I have always had just separate vehicles around the base, I could never attach things together without all kinds of problems. I will definitely give this a try. Thank you for your incredible work and clear insights on how to do this!!

[togfox]

I will definitely give this a try.

Make sure you report back how awesome the new hydraulic legs are while building this.

[hobbsyoyo]

Make sure you report back how awesome the new hydraulic legs are while building this.

Yes, this please. I am sketching out a laythe base and I would love to know if the new landing legs will mess up the design.

[Kulebron]

Let's have some pictures first to fire up the imagination:

Mun Fuel Terminal:

I see Tour Eiffel! Très bien! Admirablement!

[Oznerol256]

Make sure you report back how awesome the new hydraulic legs are while building this.

They are not awesome at all. In fact, i have found the LT-2 legs to be far too weak to be used for anything at all, at least on planets with some gravity. Mun or Minmus might work, i didnt test it.

I just don't want to launch something that got such a test result: http://forum.kerbalspaceprogram.com/threads/53664-New-Landing-Legs

[togfox]

Yes, this please. I am sketching out a laythe base and I would love to know if the new landing legs will mess up the design.

My hidden sarcasm was a clue that the new hyrdaulic legs no longer have a fixed length. They change depending on the weight of the module. What this means is unless you use legs of fixed length this modular system no longer works.

Not knocking squad or the legs. I think they're a step forward. I'm just pointing out we need to adjust strategies to make this modular system work.

[hobbsyoyo]

I got the sarcasm, I was asking him to share any data he has on how to adjust strategies for the new legs.

[togfox]

I'm going to investigate a way to attached those fixed length structural beam thingy's underneath the modules. They will need to be shorter than the legs so that the legs can raise them off the ground. When the legs are raised, the modules will rest on the sctrural parts at a fixed and predictable height.

Unfortunately, driving a 'trolley' underneath the module will now be more uncertain as you can no longer be sure if the legs will raise the module to a correct height. I considered attaching my trolley to the end of the module and drive it around like a forklift. There is already a decoupler on each end of the module so this would be easy. Unfortunately the balance would be wrong and the forklift would just tip over. It will require some more brain power to come up with a solution to both 'mount' the module and move it around. I really wish a hydraulic/hinge part was available in stock like the damne robotics part. You can make genuine arms, holsters and grippy things in the stock game then.

[Pipcard]

My question is: how would you land these modules on the Mun in the first place?

[SpaceSphereOfDeath]

excellent post, huge help - i'm off to make stuff........

I'm coming with you!

Well done my good sir,

Have some Rep!

[togfox]

Make sure you report back how awesome the new hydraulic legs are while building this!

[hobbsyoyo]

My question is: how would you land these modules on the Mun in the first place?

My method is a bit difficult as I build the rovers facing forward as they would face on the ground (but is in fact sideways relative to the VAB's building orientation which is up/down) then I attach the rocket underneath them. This has the advantage of being easier to mount the rocket directly under the CoM (very hard to do if you tilt the rover on it's side so it's pointing up as the CoM will be off to the side). The disadvantage is that this breaks symmetry. When you try to build the rocket underneath it, you have to build each booster seperately.

There are probably much easier ways to do it with the subassembly tool or maybe with the SPH.

If you want to land on an airless body, attach retrorockets to the side that can decouple after touchdown. On a world with an atmosphere, attach lots of chutes to the top of the hab module and it shouldn't need retrorockets.

[Pipcard]

What about the idea of making each module have wheels?

Edited November 3, 2013 by Pipcard

[cyoung_mi]

I really like your design, seems much easier to move things around this way..

Instead of "shoving" parts or flying them.

But I'm having a problem getting new modules built and landed.

You show a large orange fuel tank with landing gear. I'd like to land one of those on Mun, but I'm not sure how.

Do you just mount engines on the side that decouple, and then edit the save to clean up the debris?

Any chance someone can post a youtube video or tutorial with screenshots?

Thanks again!